Molds are widely used for manufacturing optical articles, such as light guide plates, lenses, and so on. Referring to FIG. I, a conventional lens mold 100a includes a first mold 12, a second mold 14, a positioning element 16 and a bushing 18 for receiving the first mold 12, the second mold 14 and positioning element 16 therein.
The first mold 12 includes a first molding portion 120 extending from one end thereof The first molding portion 120 defines a first molding surface 122 and an end surface (not labeled) adjacent to the first molding surface 122. The second mold 14 includes a second molding portion 140 extending from one end thereof The second molding portion 140 defines a second molding surface 142 corresponding to the first molding surface 122 and an end surface (not labeled) adjacent the second molding surface 142. The positioning element 16 is annular shaped.
In a glass lens molding process, the second mold 14 is inserted inside the bushing 18; the positioning element 16 is placed around the second molding portion 140 of the second mold 14; then a glass preform is put on the second molding surface 142; the first mold 12 is inserted into the bushing 18 to press the glass preform, thereby obtaining a predetermined glass lens. The obtained glass lens has a center portion and a peripheral portion. According to the conventional lens mold 100a, by adjusting a distance between the first molding surface 122 and the second molding surface 142, a thickness of the center portion and the peripheral portion can be changed. Thus, a number of differing glass lenses with various thicknesses can be obtained.
However, when the distance between the first molding surface 122 and the second molding surface 142 is changed, the thickness of the center portion and that of the peripheral portion will be changed also. In pressing, a shrinkage of the center portion is different from that of the peripheral portion, so that simultaneously changing the distance between the first molding surface 122 and the second molding surface 142 will give the center portion and the peripheral portion different levels of thickness. Therefore, although the conventional lens mold 100a can adjust the thickness of the obtained glass lenses, errors will occur. In order to obtain a precise thickness change in the center portion and the peripheral portion, a mold allowing separate changing of the thickness of the center portion and of the peripheral portion is desired.
Therefore, a press-molding mold which can separately adjust the thickness of the center portion and the peripheral portion is provided.